Bill Fitzmaurice

Even 2x15 mains don't get boundary loading when up on a pole, so what a 2x15 on a pole is capable of with lows a 1x15 on the floor next to a wall will do. The #1 mistake made by PA newbies is tops that at too large, subs that are too small, or non-existent. A pair of 1x10 tops and 2x15 subs is a well balanced system.

Outdoors is a challenge due to the lack of walls. Typically it takes twice as many subs to reach the same levels as indoors. Tops don't have that problem as being directional they don't use boundary loading. The subs don't need to be centered, off to the side is fine, but they still should be clustered unless the venue size is so large that they, and the tops, are spread by at least 14 meters or so.

Because of the need for boundary loading with bass subs are a must with no backline. I'm not familiar with your subs, but most subs of that sort are pretty much the same. I can't imagine using only one. Don't worry about center clustering, it's not necessary. Just put them together close to a wall wherever they'll fit. Sub output is omni-directional and the wavelengths are too long for them to be directionally located, so they can go anywhere. They don't even need to be aimed into the room. Aiming them at a wall can improve the low end loading and filter out above pass band harmonic distortion that you don't want to hear anyway. I'm not the person to recommend new gear, though. The last time I used speakers not of my own design and making was around 1973.

Pay attention to the video with respect to the subs. They should almost never be split left/right. The exception is when they're placed at least two wavelengths apart. At 50Hz two wavelengths is roughly 14 meters. A point the video doesn't touch on is that subs should be placed less than 1/2 wavelength away from the nearest wall for best results. At 100Hz that's 1.7 meters. Having them further out costs sensitivity, and can also result in boundary reflection sourced nulls. Most bands and DJs don't place subs correctly, simply because they don't know any better. It doesn't help when manufacturers show them set up that way, and put pole sockets on top of subs that encourages putting subs exactly where they should not be. When you do that you don't have ground or wall reinforcement for the lows, probably have floor reflection response notches, and may have rear wall reflection response nulls as well. I always have my bass in the PA even though I seldom use subs, but do so only to give dispersion of the mids throughout the room. To that end I high pass the signal into the PA at 150Hz.

It's probably no worse than an average 10 on the floor, but on a pole it will be totally different. The lack of ground reinforcement will cost 6dB, the equivalent of a 75% power reduction, while floor bounce cancellation can result in a 24dB response notch. Agreed. It would probably take two 15 inch subs, or one 18, and that only makes sense if the drums are in the PA as well. Not that it's a bad idea to do so, but it's a major expense between on thing and another, while his current rig is a bird in the hand.

Those mains are intended to be used with subs to handle the lows, so without subs they probably wouldn't do. Assuming they're up on poles you don't have ground reinforcement,while you do have floor bounce cancellation of bass, which makes the situation even worse.

I've seen it before, though I can't recall on what.

+1. By and large you want to high pass the bass in the PA around 150-200Hz. That way the directional mids and highs get dispersed throughout the room by the PA, without adding lows that the backline amp will usually provide enough of. The exception would be a very large room.

Power has nothing to do with it. What determines cone excursion, which determines sound pressure level, is the amp voltage swing. A SS amp will deliver the same voltage into any impedance load, so when you add a second identical cab both will realize the same excursion. That gives a 6dB increase compared to just one. The halved impedance load results in doubling of the current draw, which results in the doubling of the power draw, but it's the doubling of cone excursion driven with equal voltage that gives the increased SPL.

Pickups are like speakers. If they had flat response they'd all sound the same.

It comes from amp voicing, which is response adjustments independent of the EQ not user adjustable.

Channel strips are designed to have flat response with the knobs at zero, otherwise they'd never pass muster in a studio. Most bass amps are designed to have a pleasing tone with the EQ at zero according to the preferences of the B testers, but with different basses, speakers and personal taste what usually prevails is the preference of the actual designer. An exception is valve amps with the classic Fender tone stack EQ, which not being active is incapable of flat. That was of no concern to Leo Fender. He didn't care what the response looked like, he just wanted it to sound good. The consensus is that he succeeded. https://robrobinette.com/How_The_TMB_Tone_Stack_Works.htm

Mixing a 115 and 410 is always a bad idea, no matter what advertising may say to the contrary.

That's up for interpretation, but in any event the thermal power rating doesn't say how much power a cab can actually make use of. It's like asking how bright is a 100 watt light bulb. That all depends. Incandescent? Sodium? Florescent? LED? We can get the real information we need on a two quid light bulb package but not on a speaker that costs upwards of a hundred times or even a thousand times that. 🙄

Most active EQs have similar plots. It doesn't show what's happening elsewhere in the amp. As to what sounds flat, you have to take into consideration both the coloration added by the speaker and the effect of equal loudness. Once you do so it's impossible to say that a particular amp sounds flat.

That still doesn't guarantee flat, as most pre-amps have some degree of pre-shape. Besides that, speakers aren't flat. Chances are if you did get truly flat you wouldn't like it anyway, as flat sounds quite sterile. I've never understood why anyone would want it flat.

If they were the same drivers in the same net cabinet volume per driver with the same tuning then all three 12s would have had the same output. Your experience shows the downside of what can happen when they're not.

The notion of using a low impedance load to 'get all the watts out of my amp' is intrinsically flawed. It assumes that what determines how loud you can go is power related. It's not. While power is part of the equation so is the speaker frequency response, sensitivity and cone displacement. There are 8 ohm 1x12s that will go louder than 4 ohm 2x10s, so unless you have the exact specs on your current speaker and any that you're considering, which isn't likely as most manufacturers don't provide them, side by side testing is the only way to know if a change is worthwhile.

They may all be 32 ohms, as is the case with the SVT, so one must be sure of it.

It was intended for use along with a TNT amp and cab as a bi-amped low frequency/high frequency rig. Another example: https://reverb.com/item/21762989-peavey-2x8-100w-powered-bass-bi-amp-cabinet-late-1980-s-early-1990-s

We've all been through this identical question.

My advice is don't double post. 🙄

Absolutely correct. The second cab will increase both sensitivity and maximum output by 6dB. That's the equivalent of quadrupling power. Chances are the 350 watt amp will deliver all the power the drivers can handle. It's the rare twelve that can make use of more than 175w before running out of excursion capacity. OTOH the number of twelves that can take 500w without exceeding their excursion capacity is small, and they're PA subwoofer drivers, not electric bass drivers.

I've been trying to call my local paint supply store but can't get a dial tone on my phone. 🙄

Awaiting the first person to ask 'What's a blackboard?'